On Tue, 2017-05-16 at 17:39 -0700, Puthikorn Voravootivat wrote:
>
>
> On Tue, May 16, 2017 at 2:21 PM, Pandiyan, Dhinakaran
> <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> On Tue, 2017-05-16 at 13:56 -0700, Puthikorn Voravootivat
> wrote:
> >
> >
> > On Tue, May 16, 2017 at 1:29 PM, Pandiyan, Dhinakaran
> > <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> > On Tue, 2017-05-16 at 11:07 -0700, Puthikorn
> Voravootivat
> > wrote:
> > >
> > >
> > > On Mon, May 15, 2017 at 11:21 PM, Pandiyan,
> Dhinakaran
> > > <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> > > On Mon, 2017-05-15 at 17:43 -0700,
> Puthikorn
> > Voravootivat
> > > wrote:
> > > >
> > > >
> > > > On Mon, May 15, 2017 at 4:07 PM,
> Pandiyan,
> > Dhinakaran
> > > > <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> > > > On Fri, 2017-05-12 at 17:31
> -0700,
> > Puthikorn
> > > Voravootivat
> > > > wrote:
> > > > >
> > > > >
> > > > >
> > > > > On Fri, May 12, 2017 at 5:12
> PM,
> > Pandiyan,
> > > Dhinakaran
> > > > >
> <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> > > > > On Thu, 2017-05-11 at
> 16:02
> > -0700,
> > > Puthikorn
> > > > Voravootivat
> > > > > wrote:
> > > > > > Read desired PWM
> frequency
> > from panel
> > > vbt and
> > > > calculate the
> > > > > > value for divider in
> DPCD
> > address 0x724
> > > and 0x728
> > > > to have
> > > > > > as many bits as
> possible for
> > PWM duty
> > > cyle for
> > > > granularity
> > > > > of
> > > > > > brightness
> adjustment while
> > the
> > > frequency is still
> > > > within
> > > > > 25%
> > > > > > of the desired
> frequency.
> > > > >
> > > > > I read a few eDP panel
> data
> > sheets, the
> > > PWM
> > > > frequencies all
> > > > > start from
> > > > > ~200Hz. If the VBT
> chooses this
> > lowest
> > > value to
> > > > allow for more
> > > > > brightness control,
> and then
> > this patch
> > > lowers the
> > > > value by
> > > > > another 25%,
> > > > > we'll end up below the
> panel
> > allowed PWM
> > > frequency.
> > > > >
> > > > > In fact, one of the
> systems I
> > checked had
> > > PWM
> > > > frequency as
> > > > > 200Hz in VBT
> > > > > and the panel
> datasheet also had
> > PWM
> > > frequency range
> > > > starting
> > > > > from
> > > > > 200Hz. Have you
> considered this
> > case?
> > > > >
> > > > > The spec said "A given LCD
> panel
> > typically has a
> > > limited
> > > > range of
> > > > > backlight frequency
> capability.
> > > > > To limit the programmable
> frequency
> > range,
> > > limitations are
> > > > placed on
> > > > > the allowable total divider
> ratio with
> > the Sink
> > > device"
> > > > > So I think it should be auto
> cap to
> > 200Hz in this
> > > case.
> > > > >
> > > > > -DK
> > > > > >
> > > > > > Signed-off-by:
> Puthikorn
> > Voravootivat
> > > > <puthik@xxxxxxxxxxxx>
> > > > > > ---
> > > > > >
> > >
> drivers/gpu/drm/i915/intel_dp_aux_backlight.c |
> > > > 81
> > > > >
> +++++++++++++++++++++++++++
> > > > > > 1 file changed, 81
> > insertions(+)
> > > > > >
> > > > > > diff --git
> > > >
> > a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > > >
> > >
> b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > > > > index
> > 0b48851013cc..6f10a2f1ab76 100644
> > > > > > ---
> > > >
> > a/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > > > > +++
> > > >
> > b/drivers/gpu/drm/i915/intel_dp_aux_backlight.c
> > > > > > @@ -113,12 +113,86
> @@
> > > > >
> > >
> intel_dp_aux_set_dynamic_backlight_percent(struct
> > > > intel_dp
> > > > > *intel_dp,
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > +/*
> > > > > > + * Set PWM
> Frequency divider
> > to match
> > > desired
> > > > frequency in
> > > > > vbt.
> > > > > > + * The PWM
> Frequency is
> > calculated as
> > > 27Mhz / (F
> > > > x P).
> > > > > > + * - Where F = PWM
> Frequency
> > > Pre-Divider value
> > > > programmed
> > > > > by field 7:0 of the
> > > > > > + *
> > EDP_BACKLIGHT_FREQ_SET
> > > register
> > > > (DPCD
> > > > > Address 00728h)
> > > > > > + * - Where P =
> 2^Pn, where Pn
> > is the
> > > value
> > > > programmed by
> > > > > field 4:0 of the
> > > > > > + *
> > EDP_PWMGEN_BIT_COUNT
> > > register
> > > > (DPCD Address
> > > > > 00724h)
> > > > > > + */
> > > > > > +static void
> > > intel_dp_aux_set_pwm_freq(struct
> > > > > intel_connector
> *connector)
> > > > > > +{
> > > > > > + struct
> drm_i915_private
> > *dev_priv
> > > =
> > > > >
> to_i915(connector->base.dev);
> > > > > > + struct
> intel_dp
> > *intel_dp =
> > > > >
> > >
> enc_to_intel_dp(&connector->encoder->base);
> > > > > > + int freq, fxp,
> fxp_min,
> > fxp_max,
> > > fxp_actual,
> > > > f = 1;
> > > > > > + u8 pn, pn_min,
> pn_max;
> > > > > > +
> > > > > > + /* Find
> desired value of
> > (F x P)
> > > > > > + * Note that,
> if F x P
> > is out of
> > > supported
> > > > range, the
> > > > > maximum value or
> > > > > > + * minimum
> value will
> > applied
> > > automatically.
> > > > So no
> > > > > need to check that.
> > > > > > + */
> > > > > > + freq =
> > > dev_priv->vbt.backlight.pwm_freq_hz;
> > > > > > +
> DRM_DEBUG_KMS("VBT
> > defined
> > > backlight
> > > > frequency %u Hz
> > > > > \n", freq);
> > > > > > + if (!freq) {
> > > > > > +
> > DRM_DEBUG_KMS("Use panel
> > > default
> > > > backlight
> > > > > frequency\n");
> > > > > > +
> return;
> > > > > > + }
> > > > > > +
> > > > > > + fxp =
> > > KHz(DP_EDP_BACKLIGHT_FREQ_BASE_KHZ) /
> > > > freq;
> > > > > > +
> > > > > > + /* Use highest
> possible
> > value of
> > > Pn for more
> > > > > granularity of
> brightness
> > > > > > + * adjustment
> while
> > satifying the
> > > conditions
> > > > below.
> > > > > > + * - Pn is in
> the range
> > of Pn_min
> > > and Pn_max
> > > > > > + * - F is in
> the range
> > of 1 and
> > > 255
> > > > > > + * - Effective
> frequency
> > is within
> > > 25% of
> > > > desired
> > > > > frequency.
> > > > > > + */
> > > > > > + if
> > > (drm_dp_dpcd_readb(&intel_dp->aux,
> > > > > > +
> > > > >
> DP_EDP_PWMGEN_BIT_COUNT_CAP_MIN,
> > > &pn_min) != 1) {
> > > > > > +
> > DRM_DEBUG_KMS("Failed to
> > > read pwmgen
> > > > bit count
> > > > > cap min\n");
> > > > > > +
> return;
> > > > > > + }
> > > > > > + if
> > > (drm_dp_dpcd_readb(&intel_dp->aux,
> > > > > > +
> > > > >
> DP_EDP_PWMGEN_BIT_COUNT_CAP_MAX,
> > > &pn_max) != 1) {
> > > > > > +
> > DRM_DEBUG_KMS("Failed to
> > > read pwmgen
> > > > bit count
> > > > > cap max\n");
> > > > > > +
> return;
> > > > > > + }
> > > > > > + pn_min &=
> > > DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > > > > > + pn_max &=
> > > DP_EDP_PWMGEN_BIT_COUNT_MASK;
> > > > > > +
> > > > > > + fxp_min = fxp
> * 3 / 4;
> > > > > > + fxp_max = fxp
> * 5 / 4;
> > > > >
> > > > >
> > > > > You are allowing fxp
> between +/-
> > 25% of
> > > the actual.
> > > > This isn't
> > > > > same as
> > > > > the "Effective
> frequency is
> > within 25% of
> > > desired
> > > > frequency."
> > > > > right? The
> > > > > frequency can vary
> between -20%
> > and +33%.
> > > > >
> > > > >
> > > > > You are right.
> > > > > You want me to change commit
> message to
> > reflect
> > > this or
> > > > change the
> > > > > code to
> > > > > match the commit message?
> > > >
> > > >
> > > > I am okay with fixing the
> comment and
> > commit
> > > message. Is the
> > > > 25%
> > > > arbitrary or based on the
> distances
> > between the
> > > possible
> > > > values? Please
> > > > make a note in the comment if
> it's the
> > former.
> > > >
> > > >
> > > > > > + if (fxp_min <
> (1 <<
> > pn_min) ||
> > > (255 <<
> > > > pn_max) <
> > > > > fxp_max) {
> > > >
> > > >
> > > >
> > > > > > +
> > DRM_DEBUG_KMS("VBT defined
> > > backlight
> > > > frequency
> > > > > out of range\n");
> > > > > > +
> return;
> > > > > > + }
> > > > > > +
> > > > > > + for (pn =
> pn_max; pn >
> > pn_min;
> > > pn--) {
> > > >
> > > > Is there a reason this is not pn
> >=
> > pn_min?
> > > > This is bug because f value will be
> incorrect in
> > the case
> > > that pn ==
> > > > pn_min.
> > > > Thanks for catching this.
> > > >
> > >
> > >
> > > Isn't that a side-effect using the right
> shift
> > operation for
> > > division?
> > > The bug is just for loop that exit too soon.
> > >
> >
> > Not sure I got that, what's the invalid "f" case
> that you see
> > with
> > pn==pn_min?
> >
> >
> >
> > if the for loop has pn > pn_min, when pn == pn_min we will
> exit the
> > loop first
> > without running the f = clamp(fxp >> pn, 1, 255); in the
> next line.
> >
> >
> > This would fix with pn >= pn_min in for loop.
> >
>
>
> Ah! I thought you were giving me a reason to not change it to
> pn >=
> pn_min .
>
>
> >
> > We guarantee that the break statement will be called and pn
> won't be
> > pn_min - 1
> > because we check (fxp_min < (1 << pn_min) || (255 << pn_max)
> <
> > fxp_max) before
> > entering this for loop.
> >
> >
> >
> > > Would DIV_ROUND_CLOSEST allow you to use
> pn_min?
> > > It does not related to the point above, but
> > DIV_ROUND_CLOSEST still
> > > better than just using right shift. I will change
> to that in
> > next
> > > version.
> > >
> > >
> > > >
> > > > > > + f =
> clamp(fxp >>
> > pn, 1,
> > > 255);
> > > > > > +
> fxp_actual = f
> > << pn;
> > > > > > + if
> (fxp_min <=
> > fxp_actual
> > > &&
> > > > fxp_actual <=
> > > > > fxp_max)
> > > > > > +
> break;
> > > > > > + }
> > > > > > +
> > > > > > + if
> > > (drm_dp_dpcd_writeb(&intel_dp->aux,
> > > > > > +
> > > > DP_EDP_PWMGEN_BIT_COUNT, pn) <
> > > > > 0) {
> > > > > > +
> > DRM_DEBUG_KMS("Failed to
> > > write aux
> > > > pwmgen bit
> > > > > count\n");
> > > >
> > > >
> > > > If the number of brightness
> control bits
> > are
> > > changing, the
> > > > max.
> > > > brightness value changes too.
> > > >
> > > > Please see
> intel_dp_aux_setup_backlight().
> > > >
> > > >
> > > > I think this is fine because
> > > > - intel_dp_aux_setup_backlight() will
> > > > called intel_dp_aux_enable_backlight()
> which
> > > > called intel_dp_aux_set_pwm_freq() first
> before
> > determine
> > > the max
> > > > brightness value.
> > > > - Also, the panel I tested does not
> change
> > > > BACKLIGHT_BRIGHTNESS_BYTE_COUNT
> > > >
> > > > when changing the frequency.
> > >
> > >
> > > The only values I see being set for max
> brightness
> > are 0xFFFF
> > > and 0xFF
> > >
> > > if (intel_dp->edp_dpcd[2] &
> > > DP_EDP_BACKLIGHT_BRIGHTNESS_BYTE_COUNT)
> > > panel->backlight.max = 0xFFFF;
> > > else
> > > panel->backlight.max = 0xFF;
> > >
> > > I can't see where you are setting this
> based on Pn.
> > Can you
> > > please point
> > > out? From what I understand, max should be
> 2^Pn.
> > >
> > >
> > > It is suppose to be 0xFF or 0xFFFF only.
> > >
> > >
> > > From eDP spec:
> > > 0x702 bit 2 BACKLIGHT_BRIGHTNESS_BYTE_COUNT
> > > 0 = Indicates that the Sink device supports a
> 1-byte setting
> > for
> > > backlight brightness
> > > 1 = Indicates that the Sink device supports a
> 2-byte setting
> > for the
> > > backlight brightness
> > >
> > >
> > > 0x722 EDP_BACKLIGHT_BRIGHTNESS_MSB
> > > The actual number of assigned bits for the
> backlight
> > brightness PWM
> > > generator is set by
> > > field 4:0 of the EDP_PWMGEN_BIT_COUNT register
> (DPCD Address
> > 00724h).
> > > Assigned bits are allocated to the MSB of the
> enabled
> > register
> > > combination
> > >
> >
> > ^This makes it somewhat clear but gets confusing
> again.
> > >
> > > This means that if PWM_GEN_BIT_COUNT is less than
> 16 then
> > the panel
> > > will ignore
> > > the least significant bit in
> EDP_BACKLIGHT_BRIGHTNESS
> > register.
> > >
> > >
> > > For example,
> > > if BACKLIGHT_BRIGHTNESS_BYTE_COUNT == 1 and
> > PWM_GEN_BIT_COUNT = 16
> > > and EDP_BACKLIGHT_BRIGHTNESS == 0xabcd
> > > In this case, all bits in EDP_BACKLIGHT_BRIGHTNESS
> will be
> > used.
> > >
> > > 0xabcd means 0xabcd / 0xffff or (43981 / 65535) or
> 67.111%
> > >
> > >
> > > if BACKLIGHT_BRIGHTNESS_BYTE_COUNT == 1 and
> > PWM_GEN_BIT_COUNT = 12
> > > and EDP_BACKLIGHT_BRIGHTNESS == 0xabcd
> > >
> > > In this case, the last 4 bits will be discarded.
> > > 0xabcd means 0xabc / 0xfff or 2748 / 4095 or
> 67.106%
> > >
> > >
> > > I think it should be fine to just have 8 or 16
> bits of the
> > max
> > > brightness and let panel drop
> > > the unneed bit to simplify the driver code.
> > >
> >
> > Note:
> > The number of assigned or controllable bits will
> have the
> > ability to
> > provide full brightness control. Examples:
> > •
> > For 10-bit operation, 000h = 0% brightness, and
> 3FFh = 100%
> > brightness.
> >
> > Going by the logic you stated, for a 10-bit control,
> the MSB
> > and LSB
> > registers have to be written FFFFh to set 100%
> brightness with
> > the last
> > 6 bits dropped off by the hardware.
> >
> > I don't like the way the spec leaves this to
> interpretation.
> > Have you
> > experimented with both 0x0ABC and 0xABCD for the
> 12-bit,
> > BYTE_COUNT==1
> > example you gave?
> >
> > Yes, already test with the real panel.
> >
> >
> > Here is better test case than 0xABCD
> > 0xFFFF with 6, 12, 16 shows very bright screen with same
> brightness in
> > all case. (All 100%)
> > 0x0FFF with 6, 12, 16 bits shows dim screen. 6 bit case is
> slightly
> > dimmer than other case.
> > Note that the brightness are 4.76% / 6.23% / 6.25% in 6 /
> 12 / 16 bits
> > case.
> >
>
>
> Great! Thanks for confirming.
>
> > You can apply this patch for easy testing
> > https://patchwork.kernel.org/patch/6241481/
> >
> >
> >
> > >
> > >
> > > Also, won't this function be called every
> time
> > > _enable_backlight() is
> > > called? Isn't doing this from setup
> sufficient? I
> > guess,
>
> I looked at this a bit and look like we need to call this every time
> _enable() is called.
> One panel that I have reset the DP_EDP_PWMGEN_BIT_COUNT (pn) to the
> lowest value
> every time panel backlight is turned off. So doing this from setup is
> insufficient.
Thanks for checking. I think, we can still avoid doing these every time
a) DPCD reads for PWM_BIT_COUNT_CAP_{MAX,MIN}
b) recomputing pn and f
-DK
>
> > > fixing it is an
> > > optimization that'd be nice to have but
> not
> > necessary.
> > >
> > > Lets get this patch set done first. I can send in
> another
> > patch after
> > > this is go in to optimize this.
> >
> > Sure. This patch should be good to go with answers
> to my
> > questions. The
> > only thing remaining would be getting an ACK from
> Jani for
> > adding a new
> > parameter for dynamic backlight control.
> >
> >
> > -DK
> >
> > > Probably need to add new member in struct
> drm_i915_private
> > >
> > > >
> > > >
> > > > > > +
> return;
> > > > > > + }
> > > > > > + if
> > > (drm_dp_dpcd_writeb(&intel_dp->aux,
> > > > > > +
> > > > DP_EDP_BACKLIGHT_FREQ_SET, (u8)
> > > > > f) < 0) {
> > > > > > +
> > DRM_DEBUG_KMS("Failed to
> > > write aux
> > > > backlight
> > > > > freq\n");
> > > > > > +
> return;
> > > > > > + }
> > > > > > +}
> > > > > > +
> > > > > > static void
> > > intel_dp_aux_enable_backlight(struct
> > > > > intel_connector
> *connector)
> > > > > > {
> > > > > > struct
> intel_dp
> > *intel_dp =
> > > > >
> > >
> enc_to_intel_dp(&connector->encoder->base);
> > > > > > uint8_t
> dpcd_buf = 0;
> > > > > > uint8_t
> new_dpcd_buf =
> > 0;
> > > > > > uint8_t
> > edp_backlight_mode = 0;
> > > > > > + bool freq_cap;
> > > > > >
> > > > > > if
> > > (drm_dp_dpcd_readb(&intel_dp->aux,
> > > > > >
> > > >
> DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > > > &dpcd_buf) != 1) {
> > > > > > @@ -151,6 +225,10 @@
> static
> > void
> > > > >
> > intel_dp_aux_enable_backlight(struct
> > > intel_connector
> > > > > *connector)
> > > > > >
> > DRM_DEBUG_KMS("Enable
> > > dynamic
> > > > brightness.\n");
> > > > > > }
> > > > > >
> > > > > > + freq_cap =
> > intel_dp->edp_dpcd[2] &
> > > > >
> > DP_EDP_BACKLIGHT_FREQ_AUX_SET_CAP;
> > > > > > + if (freq_cap)
> > > > > > +
> new_dpcd_buf |=
> > > > >
> > DP_EDP_BACKLIGHT_FREQ_AUX_SET_ENABLE;
> > > > > > +
> > > > > > if
> (new_dpcd_buf !=
> > dpcd_buf) {
> > > > > > if
> > > >
> (drm_dp_dpcd_writeb(&intel_dp->aux,
> > > > > >
> > > >
> DP_EDP_BACKLIGHT_MODE_SET_REGISTER,
> > > > > new_dpcd_buf) < 0) {
> > > > > > @@ -158,6 +236,9 @@
> static
> > void
> > > > >
> > intel_dp_aux_enable_backlight(struct
> > > intel_connector
> > > > > *connector)
> > > > > > }
> > > > > > }
> > > > > >
> > > > > > + if (freq_cap)
> > > > > > +
> > > >
> intel_dp_aux_set_pwm_freq(connector);
> > > > > > +
> > > > > >
> > set_aux_backlight_enable(intel_dp,
> > > true);
> > > > > >
> > > intel_dp_aux_set_backlight(connector,
> > > > >
> > connector->panel.backlight.level);
> > > > > > }
> > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > > >
> > _______________________________________________
> > > > > Intel-gfx mailing list
> > > > >
> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > > >
> > >
> >
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > > >
> > > >
> > > >
> > > >
> _______________________________________________
> > > > Intel-gfx mailing list
> > > > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > > >
> >
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > >
> > >
> > >
> > >
> > > _______________________________________________
> > > Intel-gfx mailing list
> > > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > >
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >
> >
> >
> >
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>
>
>
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